The purpose of this project has been 1) to determine whether acupuncture analgesia can be reliable demonstrated in human laboratory research involving painful tooth pulp stimulation, 2) to determine whether such analgesia reflects a loss in the sensory capabilities of the subject or whether it is a psychological/attitudinal change, and 3) to explore possible mechanisms of acupuncture analgesia. Our early work examined the effects of acupunctural stimulation on the ability of subjects to perceive painful electrical shocks delivered to tooth pulp. Acupuncture in the hands significantly reduced perceptual sensitivity and increased response bias, or attitudes against reporting the shocks as painful. This phenomenon was replicated in a second study and it was shown that transcutaneous electrical stimulation (TES) had the same effect when given at the acupuncture site. Another study examined the effects of acupunctural stimulation in the second trigeminal nerve division on dental pain perception. Substantial analgesia occurred, and this effect was mainly sensory loss, with no significant psychological/attitudinal alterations. We were also able to demonstrate that TES yields the same result when carried out at the same sites. We hypothesized that acupuncture and related treatments such as TES might work by causing the release of an endogenous opioid substance which can be bind to opiate receptor sites in the brain. To test this, we demonstrated TES analgesia in two groups of subjects and administered either naloxone, a morphine antagonist, or a placebo, maintaining double-blind conditions. Naloxone partially reversed the analgesia while the placebo had no effect. This suggests that endogenous opiates are implicated in the productions of acupuncture analgesia and related phenomena. We continue to pursue this line of investigation. BIBLIOGRAPHIC REFERENCES: Chapman, C.R., Gehrig, J.D., and Wilson, M.E.: Acupuncture, Pain and Signal Detection Theory. Science 189: 65, (July 4) 1976. Chapman, C.R., Wilson. M.E. and Gehrig, J.D.: Comparative effects of acupuncture and transcutaneous stimulation on the perception of painful dental stimuli. Pain 2: 265-283, 1976.